Impact of the Carbon Coating Thickness on the Electrochemical Performance of LiFePO[sub 4]/C Composites

Abstract

The electrochemical performance of LiFePO 4 /C composites in lithium cells is closely correlated to pressed pellet conductivities measured by AC impedance methods. These composite conductivities are a strong function not only of the amount of carbon, but of its structure and distribution. Ideally, the amount of carbon in composites should be minimal (less than about 2 wt. %) so as not to decrease the energy density unduly. This is particularly important for plug-in hybrid electric vehicle applications (PHEVs) where both high power and moderate energy density are required. Optimization of the carbon structure, particularly the sp 2 /sp 3 and D/G (disordered/graphene) ratios, improves the electronic conductivity while minimizing the carbon amount. Manipulation of the carbon structure can be achieved via the use of synthetic additives including iron-containing graphitization catalysts. Additionally, combustion synthesis techniques allow co-synthesis of LiFePO 4 and carbon fibers or nanotubes, which can act as "nanowires" for the conduction of current during cell operation.

All‐Solid‐State Lithium‐Ion Microbatteries: A Review of Various Three‐Dimensional Concepts

“…It has also shown to be effective as thin fi lm electrode, which can be deposited by pulsed laser deposition [ 61 , 62 ] and sputter deposition. [63][64][65] Sol-gel techniques have been applied to form LiFePO 4 powders, [66][67][68][69] but this method can possibly be extended to thin fi lm deposition.…”

Modified Pechini Synthesis of Oxide Powders and Thin Films

“…A carbon coating on the particle surfaces is typically necessary to mitigate this issue (Dominko et al 2005). Sometimes this is obtained by adding a polymer, like polyethylene glycol, to the solution, followed by a heat treatment in reducing atmosphere (Mei et al 2012).…”

Modeling the Effects of the Cathode Composition of a Lithium Iron Phosphate Battery on the Discharge Behavior

“…Despite the numerous advantages of LFP, its low electronic and ionic conductivities seriously limit its rate capability [2][3][4]. To overcome these limitations, many studies have been carried out, including particle size reduction [5][6][7], coating [8][9][10], and doping [11][12][13]. Even though the proper fabrication process of LFP has been identified, the composition of a LFP cathode consisting of active material, conductive additives, and binders should be optimized in order to tailor the LFP battery to a specific application.…”

“…Others [19][20][21][22] used or modified the model of Doyle et al [18]. Kwon et al [23] presented a different approach from the rigorous porous electrode model [6][7][8][9][10] to predict the discharge behavior of a LIB cell. They developed a model to calculate the potential and current density distribution on the electrodes of a LIB cell on the basis of charge conservation.…”